Plants do not have a central nervous system and therefore cannot receive a pain signal the way that humans receive pain signals. However, several studies have shown that plants may have different mechanisms for showing feelings.
Some scientific studies have shown that plants respond to different stimuli and change their behavior accordingly. A plant receives chemical signals from everything it comes into contact with. A caterpillar chewing on a leaf sends a different signal than a bee landing on a flower to be pollinated. The plant can trigger different responses based on the chemical signals it receives from these interactions. If a plant is being eaten by an insect, certain defense mechanisms may be triggered. One defense mechanism plants contain is the ability to send a chemical message through the air, a cry for help, to potential predators of the organisms eating them.
Other studies indicate that plants can change their growth habits based on the feelings of people caring for them. In one study, a group of plants were watered by a person with a lot of aggressive, angry energy. Another day, the same group of plants were watered by a different person with a very calm, peaceful energy. The scientists were able to detect changes in the behavior of the plants based on which person entered the room.